P1311: GRANULOCYTE COLONY-STIMULATING FACTOR MOBILIZATION FACILITATES ANTI-GRAFT-VERSUS-HOST DISEASE AND GRAFT-VERSUS-LEUKEMIA EFFECTS OF MUCOSA-ASSOCIATED INVARIANT T CELLS THROUGH DISTINCT FUNCTIONAL SUBSE
Authors: M. Gao, Y. Sun, J. Kong, Y. Chang, Y. Wang, X. Huang, X. Zhao
Journal: HemaSphere (2022)

Background: Graft-versus-host disease (GVHD) and relapse after allogeneic hematopoietic stem cell transplantation (allo-HSCT) are the main reasons leading to transplantation failure and affecting the survival of patients. Granulocyte-colony stimulating factor (G-CSF) is used to mobilize stem cells in healthy donors and promote T cell hyporesponsiveness and polarization of T cells from Th1 to Th2. Mucosal-associated invariant T cells (MAITs) are a group of multifunctional innate immune T cells, which can be activated through TCR-dependent or independent pathways, and tight integration of these signals is critical for triggering one function versus another. MAITs can exert anti-gut GVHD effects by expressing mucosal protective factors such as IL-17, while activated MAITs have certain anti-tumor effects by expressing cytotoxic factors. The two seemingly contradictory functions appear to be segregated in two distinct subsets expressing T-bet or RORγt. Taken together, G-CSF mobilization in transplantation is a critical factor affecting the cellular composition of the infused grafts. However, the effects of G-CSF on the differentiation of MAITs to various subsets and the exertion of different effector functions remain to be further elucidated. Thus, we aimed to explore the effect of G-CSF mobilization on the anti-GVHD or GVL effect of MAITs. Aims: We aimed to explore the effect of G-CSF mobilization on the anti-GVHD or GVL effect of MAITs. Methods: MAITs from peripheral blood (PB) of 4 healthy donors before and after G-CSF mobilization were analyzed by single-cell RNA sequencing (RNA-seq) and PB from 16 healthy donors before and after G-CSF mobilization was tested by flow cytometry (FCM). In vitro experiment was performed to observe the effect of G-CSF mobilization on the anti-tumor effect of MAITs. Results: First, data showed that MAITs were clustered in 13 clusters (Figure 1A and 1B), of which Cluster 1 exhibited high expression of cytotoxic molecules, including GZMA, GZMB, GZMK, and NKG7, which might be the most important anti-tumor effector subsets. And T-bet+IFN-γ+MAITs were mainly enriched in Cluster 1, which also suggested that Cluster 1 was the main effector MAIT1 subset. Second, G-CSF mobilization may promote the distribution of MAITs to cluster 1, and prompt MAITs to differentiate into T-bet+MAIT (MAIT1) that exert GVL effects and GATA3+MAIT (MAIT2) that have immunomodulatory effects, but the GVL effect of MAIT1 was limited to a certain extent, showing a state of hyporesponsiveness or inhibitory that the main effectors IFN-γ was at low expression and the inhibitory markers PD-1 and TIGIT was at high expression compared with pre-G-CSF. In terms of effector expression, G-CSF mobilization had a trend toward MAIT2 polarization (Figure 1C). In contrast, compared with pre-G-CSF mobilization, there was no significant change in RORγt+MAIT (MAIT17), but the increased expression of chemokine receptors (CCR6, CXCR3) after mobilization, which suggested that MAIT17, once activated by specific stimulatory signals, enhanced chemotaxis to inflammation or specific tissues. Finally, in vitro mixed culture of MAITs and K562, results showed that the stimulated MAITs had a certain anti-tumor effect, but G-CSF mobilization had no obvious effect on the enhancement or weakening of anti-tumor function. Image:Summary/Conclusion: G-CSF mobilization facilitates the segregation of MAITs anti-GVHD and GVL dual effects, inducing immune tolerance while promoting differentiation of GVL effector subsets, while maintaining or increasing the initiation of anti-GVHD effect.